Prof. M. Schultze on Polytrema miniaceum. 417 



(Heligoland; Northumberland, according to Hancock) it is 

 scarcely possible to find an oyster-shell or a piece of limestone 

 which is not completely riddled by Cliona. In any case the 

 parasitism of a Sponge in Polytrema presents nothing remark- 

 able ; and the next question is, whether the form and arrange- 

 ment of the spicules support the notion that they belong to a 

 Sponge like Cliona. Of the spicules of Cliona celata, which 

 occurs in particular abundance in oyster-shells on Heligoland, 

 Lieberkiihn says that they are knobbed at one end, but that 

 " frequently a very short point projects beyond the knob ; and 

 an inflation of the middle of the spicule also occurs, although 

 extremely rarely." This is all that I can learn as to the forms 

 of the spicules in the Clion^e. Unfortunately it does not suffice 

 for the discrimination of a siliceous Sponge ; for knobbed spicules 

 are common to many species, and often associated with ordinary 

 awl-shaped spicules. The greater part of the spicules of our 

 PolyiremaSponge are subulate at both ends, as shown in PL VII. 

 fig. 10. Many are broad; but the small forms resembling a 

 clasp or cramp (fig. 10 a) are rare. Capitate spicules also occur, 

 in which the axial canal, which is wanting in no siliceous spi- 

 cule, presents an inflation in the knob. All the spicules are 

 comparatively short, so that they extend at the utmost through 

 two or three chambers of the Polytrema. A few fragments of 

 larger spicules that I have seen, as also the extremely rare and 

 likewise fragmentary calcareous spicules which are sometimes 

 observed, I should regard as accidental admixtures. The short 

 subulate spicules frequently lie parallel to each other in groups, 

 as they are found in situ in Sponges. 



The preceding statements suffice, in my opinion, to prove 

 that, when siliceous spicules occur in the shells of Polythalamia, 

 together with the organic contents of the chambers, the notion 

 that in such cases we have before us transition forms between 

 Foraminifera and Porifera has but little probability in it. The 

 question now is, whether, in the case of Carpenteria, in which, 

 according to Gray and Carpenter, a Foraminiferous structure of 

 the calcareous shell and an occupation of the chambers by sili- 

 ceous spicules also occur, there is any more reason to uphold the 

 view promulgated by the English zoologists. Carpenter^s de- 

 scription of the Polythalamian named after him, which is found 

 living parasitically upon various marine productions, and espe- 

 cially numerous upon a fragment of a Porites, is, like all his 

 works upon Polythalamia, so careful and accurate that we can 

 obtain from it a perfectly clear idea of the structures in question. 

 I am therefore the more confirmed in my opinion, because there 

 does not appear to me to be the least reason for conceiving the 

 relation between the sponge-spicules and the calcareous shell in 



